Brown rice is a richer source of nutrients compared to polished white rice, and contains a majority of nutrients we need. In particular, brown rice contains high levels of dietary fiber, vitamin Bs and vitamin E whose physiological benefits are drawing the attention in recent years (refer to Patent Literature 1, Patent Literature 2, etc.).
While being an excellent food material as described above, brown rice has several drawbacks owing to the fact that its surface is covered by the so-called “bran layer,” which forms a hard outer layer containing a lot of oil and fiber. Since the aforementioned outer layer prevents heat permeation and water absorption when brown rice is cooked at normal pressures, starch does not gelatinize sufficiently, and the outer layer structure does not soften or break down sufficiently. For these reasons, brown rice cooked at normal pressures is hard and dry, and is therefore considerably less tasteful compared to polished white rice after cooking. To resolve these drawbacks, brown rice is commonly cooked under higher pressures. However, higher pressures cause vitamins and certain other nutrients vulnerable to high temperatures and pressures to partially break down, and heating until the outer layer of brown rice becomes soft causes other parts of rice to gelatinize. As a result, it has been difficult to produce high-quality brown rice that has good sensation in the mouth and is effectively digested/absorbed when cooked.
It is known that soft cooked brown rice can be obtained by soaking brown rice for an appropriate time in warm water of temperatures between 5 and 50° C., or more preferably between 20 and 40° C., to cause the rice to germinate, and then cooking this germinated rice at normal or higher pressures (Patent Literature 3). This germinated brown rice, or brown rice that underwent the germinating operation and is showing signs of germinating as a result, is called “germinated brown rice” or “germinated rice,” and is clearly differentiated from brown rice. However, the germinating process of brown rice causes the rice to lose constituents that contribute to good rice taste, either through the metabolic action of brown rice itself or due to water existing on the exterior surface of the rice. Also, growth of bacteria in the brown rice triggers fermentation, thus generating fermentation smell or other foul smell that will remain with the rice. Also with such germinated brown rice, breakdown of starch and other constituents progresses excessively over time due to the action of enzymes contained in the rice, which consequently reduces the quality of rice as food material.
To resolve the aforementioned problems, various methods have been attempted to germinate brown rice, such as using warm water containing bactericidal agent or weak electrolytic salt water; using running water; or using warm water and replacing it periodically (Patent Literature 4). However, use of chemicals such as bactericidal agent presents problems in terms of negative effects from residual substances and retention of chemical odor. Also, the method to germinate brown rice in warm water under periodic replacement or in running water results in a lot of wasted water and energy, and requires complex manufacturing controls. Patent Literature 6 discloses a technology to germinate brown rice under an environment of 100% humidity, but this technology still does not make germinating easy, and brown rice must be given warm-water shower in an interim stage, as described in Patent Literature 6. As a result, this technology fails to improve the taste and cooking property of brown rice.
Another method being employed is to germinate brown rice and then dry the rice. However, brands of dry germinated brown rice on the market exhibit a common problem, which is that the brown rice absorbs water in the germinating process and the swollen germinated rice cracks in the drying process. Cracked rice is not tasty when cooked. The inventors earlier proposed a method to heat, in a humid environment, germinated brown rice immediately after germinating (Patent Literature 5).
Following the aforementioned earlier invention, the inventors have continued their study and development in earnest to provide germinated brown rice offering improved taste and cooking property and eventually come up with an effective solution, which is proposed in the present invention.    Patent Literature 1: Japanese Patent Laid-open No. Hei 8-280394    Patent Literature 2: Japanese Patent Laid-open No. 2003-219847    Patent Literature 3: Japanese Patent Laid-open No. 2000-050818    Patent Literature 4: Japanese Patent Laid-open No. 2000-217520    Patent Literature 5: Japanese Patent No. 3423931    Patent Literature 6: Japanese Patent Laid-open No. 2002-291423